Onyx is a banded variety of the oxide mineral chalcedony. It can occur in nearly every color, most commonly with bands of black and/or white. It is a gemstone found in various regions of the world including Yemen, Uruguay, China, Czech Republic, Germany, Indonesia, the UK, and various states in the US. Black Onyx is the most common variety, along with white and red colors. The red variety is known as Sardonyx. The ancient Romans entered battle carrying amulets of Sardonyx engraved with Mars, the god of war. This was believed to bestow courage in battle. In Renaissance Europe, wearing Sardonyx was believed to bestow eloquence. Sardonyx was traditionally used by English midwives to ease childbirth by laying it between the breasts of the mother.